
state database and a level 2 link-state database, in much the same way that an OSPF ABR must
maintain a separate database for each area to which it is attached. Cisco routers are configured
as L1-only, L2-only, or L1/L2 with the command is-type. By default, they are L1/L2.
Note: In actuality, routers R4 and R5 would also make up the part of the backbone, but since they
are not given as choices the best answer is E.
QUESTION NO: 7
Which two statements are true about IS-IS routing? (Choose two.)
A. Based on the default timers, OSPF detects a failure faster than IS-IS does.
B. OSPF default timers permit more tuning than IS-IS does.
C. IS-IS is more efficient than OSPF in the use of CPU resources.
D. OSPF is more scalable than IS-IS because of its ability to identify normal, stub, and NSSA
areas.
E. IS-IS and OSPF are both Open Standard, link-state routing protocols which support VLSM.
Answer: C,E
Explanation:
IS-IS is the dynamic link-state routing protocol for the OSI protocol stack. As such, IS-IS
distributes routing information for routing CLNP data for the ISO CLNS environment. When IS-IS is
used strictly for the ISO CLNS environment, it is referred to as ISO IS-IS.
Differences between IS-IS and OSPF
Although IS-IS and OSPF share many common features, they do have quite a few differences:
* Whereas OSPF routers can be part of multiple areas, an IS-IS router belongs to only one area
per routing process.
*
* In OSPF, the boundaries of areas are set in the router. The boundaries of areas are on the
network connections between routers for IS-IS, reiterating that each router is in only one area per
routing process.
* IS-IS utilizes CLNS protocol data units (PDUs) to send information between routers instead of
using IP packets, like OSPF does.
* IS-IS allows for the preempting of DRs, where OSPF does not.
* OSPF DROthers do not form adjacencies with other DROthers on broadcast multi-access
networks, while in the same environment, all IS-IS intermediate systems form adjacencies with
one another.
The backbone of an IS-IS network is designated by the type of routers in it instead of being
designated by an area number (0, in the case of OSPF).
Cisco 642-901: Practice Exam
7
http://certkill.com